Haul in some clay, or mine it onsite if available, and put a cap on the woodpile.
Dump a few ton of ag lime on the pile before you cover it up, then more lime on top.
Fertilize, till, seed with grass and dutch clover.
If it's not possible to cap it off, the ag lime will at least help with the ph of the runoff coming from the pile.
Or... dig the whole mess up and get it out of your watershed, then use proper fill material to re-grade the rough site.
